In general, voice-over-Internet-Protocol (VOIP) service providers typically provision Time Division Multiplexing (TDM) facilities between TDM local switches located within the Publicly Switched Telephone Network (PSTN) and TDM-IP gateway switches located within the VOIP network. The TDM facilities are used in order to provide ingress access and egress access to PSTN endpoints, enabling the PSTN endpoints to access IP endpoints and enabling IP endpoints to access the PSTN endpoints. Unfortunately, dedicated TDM facilities do not provide the same level of resiliency to network failures that is provided by IP networks, especially for inbound traffic originating from PSTN endpoints and terminating on IP endpoints.
For such ingress traffic originating from PSTN endpoints, service providers must typically provision subscriber telephone numbers on the TDM local switches. The TDM local switches then map each of the subscriber telephone numbers to the address of at least one TDM-IP gateway switch deployed within the VOIP network. The TDM facilities are then provisioned between TDM local switches within the PSTN and TDM-IP gateway switches within the VOIP network in order to route both signaling and media traffic between the PSTN network and the VOIP network.
Unless a VOIP service provider invests in redundant TDM facilities between the TDM local switches and the associated TDM-IP gateway switches, unavailability of a required TDM facility between a TDM local switch and a TDM-IP gateway switch will prevent the completion of connections between the PSTN endpoints and IP endpoints. Unfortunately, the expense and complexity associated with deploying redundant TDM facilities makes the use of such redundant TDM facilities prohibitive. This is especially true for VOIP service providers interfacing with a large number of TDM local switches.
Accordingly, a need exists in the art for a method and apparatus for establishing a media path between a TDM-IP gateway switch and a border element such that reliance on TDM facilities between TDM local switches and TDM-IP gateway switches is minimized.